What this snippet does
Replacing a method with an arrow function detaches it from the instance's 'this' context, leading to undefined errors.
Expected output
TypeError: Cannot read properties of undefined (reading 'val')
Why practise typing this
Typing decorators code builds muscle memory for the symbols and indentation TypeScript uses most, which prose-based typing tests never cover. DevType measures your words per minute and accuracy on this snippet and tracks the individual characters you mistype, so later lessons can target them.
More TypeScript practice
- Applying a basic class decoratorDecorators · advanced
- Injecting metadata into a classDecorators · advanced
- Decorator returning an invalid typeDecorators · advanced
- Logging method calls with a decoratorDecorators · advanced
- Depracating a method safelyDecorators · advanced
- Basic property decoratorDecorators · advanced